Method of reducing ring wear in compression ignition engines burning residual hydrocarbon fuel



METHUD F REDUCING RING WEAR llN CUM. FIRESSIIUN IGNTTIUN ENGINES .1 a SlDlUAL HYDROC l. 0N FUEL Everett N. Case, Homewood, and Seymour ll-ll. Patinhin, Chicago, llL, and Hebert D, Young, Hammond, llud., assignors to Sinclair Research, Inc., Wilmington, Beth, a corporation of Delaware No Drawing. Filed June 15, 1962, Ser. No. 202,700

7 Claims. (Cl. 44-70) The present invention relates to a method of reducing wear in compression-ignition engines when burning residual fuel.

Types of fuels acknowledged as possessing characteristics most advantageous for burning in compressionignition engines, particularly from the standpoint of engine wear, are the straight run distillate type diesel fuels, having a boiling range of approximately 350725 F., characterized by low sulfur and carbon residue content of under 1.0% and 0.2% weight percent, respectively, or blends of straight run and catalytically cracked distillate stocks having about the same volatility, sulfur and carbon residue characteristics as the straight run distillates. On the other hand, the burning of residual fuels or cutback residual fuels of high sulfur and carbon residue content in relatively small bore, medium speed compression-ignition engines of the type used in freight locomotive service is known to cause excessive wear of power assembly components such as rings and liners, especially when the engine is operating under part load or idling. The reason for this is due, for the most part, to the lower gross combustion chamber temperatures prevailing plus the attendant difliculties of atomizing and completely burning heavier fuels of the residual type under these engine operating conditions.

For example, the part load ring wear resulting from the burning of residual fuels of high sulfur and carbon residue content has been reported to be as much as 25 times that obtained with economy type distillate fuels. Economy type fuels are widely used diesel fuels and usually represent blends of straight run and catalytically cracked stocks with the latter type frequently predominating. Thus, for obvious economical reasons a method of burning these residual fuels so as to obtain a reduced rate of engine wear, particularly piston ring wear, becomes highly desirable.

Residual fuels are currently being used to a limited extent in the operation of freight locomotive diesels but only under high load conditions, i.e. in seventh and eighth throttle positions. Distillate fuel is used for idle and part load operation. This method of burning residual fuel in locomotive engines is called Dual-Fuel operation. The present invention permits the employment of high sulfur, high carbon residue content residuals across the entire speed and load range of the locomotive diesel without the assistance of fuel containing only distillates for part load operation.

It has now been discovered that in a compression-ignition engine wherein a residual fuel of high sulfur and carbon residue content is burned, the piston ring wear of the engine can be substantially reduced by adding to the residual fuel prior to burning, small, effective amounts of lithium or potassium naphthenate. The actual amount of additive incorporated will be dependent on the specific star Patented Sept. 13, 11000 W at...

type and grade of residual fuel selected, the particular engine utilized, the power output at which the engine is run, etc. but in any event will be sufficient to substantially reduce the piston wear. Generally, the amount employed will fall within the range of about .05 to 0.5% by weight based on the residual fuel, but amounts up to about 1 or 2% can be employed, if desired.

The residual fuels of the type referred to in this invention can be derived from various crudes, for example, naphthenic, parafiinic and Mid-Continent crudes, and will often have a sulfur content in excess of about 1.25 weight percent and a carbon residue level in excess of about 3.5%. The residual components of such fuels are commonly obtained as still bottoms from vacuum flashed reduced crudes and as bottoms from thermal and catalytic cracking operations. Usually these residual stocks are diluted to appropriate viscosity levels by means of distillate cutter stocks to produce three grades of fuel commonly referred to as ASTM No. 4, No. 5 and No. 6 residual fuels. ASTM No. 4 grade fuels have a kinematic viscosity range at 100 F. of between about 5.8 to 26.4 centistokes. The kinematic viscosity of ASTM No. 5 grade residual fuels will range from 32.1 centistokes at 100 F. to 86.3 centistokes at 122 F. ASTM No. 6 residual fuels will have a kinematic range at 122 F. of 97.2 to 638. The API gravities of such fuels will usually range from about 6 to 30.

The type of residual fuel with which this invention is largely concerned is the ASTM No. 4 grade i.e. residual stocks diluted with 50% or more of a distillate cutter stock composed either of straight run distillate, catalytically cracked distillate, or combinations of straight run and catalytically cracked distillates. Economy diesel fuels may well represent a type of distillate fuel used for cutting back residual stocks to produce a residual diesel fuel possessing the required handling characteristics for use in freight locomotive diesel engines. Residual stocks may be cut back with appropriate distillates to give the finished product other desirable properties in addition to handling characteristics. These properties are cctane number, viscosity, pour point, sulfur and carbon residue level, volatility as well as metals content. Residual fuels as implied in this invention are blends of any type which contain residual stocks amounting to about 5% or more in volume, often about 25-80%. In one specific aspect this invention relates to the burning of residual type fuels containing about 40-60% of distillate cutter stock composed of straight run and/or catalytically cracked components.

The following example is included to further illustrate the present invention.

EXAMPLE Lithium and potassium naphthenate were separately added in concentrations of 0.25 and 0.5 by weight to a cutback residual fuel of 1.86% sulfur composed of 53.0% economy type distillate diesel fuel and 47% No. 6 residual fuel and the fuel blends tested for piston ring wear in a GM 2-71 2 cylinder, 2 stroke cycle diesel engine. The economy type distillate fuel is composed of straight run distillate fuel and 20% fluid light cycle oil. Prior to each test the base fuel i.e. without additive was also tested.

The results of the tests are shown in Table I below.

Table I Rate of ring wear with 0.5% Rate of ring Additive by weight wear on base additive, fuel, mgJhr.

mg./hr.

Lithium naphthenate:

Average reduction in wenr=approx.

roms'iiirifiipiriir'eiiii- #l 1. 77 4. 91 3. 61 5. 70 2. 56 5. 81 2. 76 5. 69 1. 85 2. 74

Rate of ring Rate of ring wear with wear on base 0.25% additive, iuel, mgJhr.

mgJhr.

Lithium naphthenate:

Agggage reduction in wear=approx. soditirh'hiipirihriiiiIIIIIIIIIIIIIIIII Iii "if Reduction in wear=approx. 6% Potassium naphthenate:

Added as a solution of 30.2% by weight of the naphthenate in mineral oil, the solution containing 10.9% free naphthenic acid and having an acid N0. of 34.

Numbers in parentheses in the table indicate the average rate of wear of the tests conducted.

The GM 2-71 diesel engine was equipped with radioactive compression rings installed in the second grooves f the pistons. The fuel system was modified slightly to permit operation on either cut-back residual fuel or on distillate fuel. The lubricating oil system of the engine is provided with a shielded monitoring well which contains a scintillation counter. The ring wear rate was determined by passing the lubricating oil through the monitoring well and therein detecting the concentration of activated iron transported to the oil due to wear of the piston rings. Prior to the running of each test fuel the engine was standardized to a constant ring wear rate with 1.0% sulfur distillate fuel. The test fuels were run either on the basis of a single 5-hour run or on a 3-hour back-tmback basis, that is, running one test fuel for 3 hours followed immediately by another test fuel for 3 hours. The back-toback basis was used when it was found that a constant wear rate could be reached in 3 hours or less. The engine was run at a load of 30 horsepower and a speed of 1200 r.p.m.

The data shows the unexpectedly superior results provided by lithium and potassium naphthenate compared to sodium naphthenate. The lithium naphthen'ate is pre ferred since it has been found to provide a much greater reduction in carbon deposits.

It is claimed:

1. A method for reducing piston ring wear in a compression-ignition engine which comprises the operation of said engine on a fuel consisting essentially of a residual fuel oil and small amounts of a compound selected from the group consisting of lithium naphthenate and potassium naphthenate, said amount being sufficient to reduce piston ring wear.

2. The method of claim 1 wherein the amount of the naphthenate is about .05 to .5 by weight.

3. The method of claim 1 wherein the residual fuel oil has a sulfur content in excess of about 1.25 weight percent.

4. The method of claim 1 wherein the fuel has an API gravity of about 6 to 30.

5. The method of claim 4 wherein the selected compound is lithium naphthcnate.

6. The method of claim 4 wherein the selected compound is potassium naphthenate.

7. The method of claim 1 wherein the residual fuel oil is diluted with 40 to by volume of a distillate cutter stock.

References Cited by the Examiner UNITED STATES PATENTS 2,068,979 l/ 1937 Fisher 252-389 2,706,149 4/1955 Brenneman 44-68 2,763,613 9/1956 Scott et a]. 44-68 2,943,925 7/1960 Ambrose 44--68 2,968,148 1/1961 Rocchini et a]. 44-68 FOREIGN PATENTS 327,289 3/ 8 Switzerland.

DANIEL E. WYMAN, Primary Examiner. W. SCHU'LZ, Y. M. HARRIS, Assistant Examiners. 

1. A METHOD FOR REDUCING PISTON RING WEAR IN A COMPRESSION-IGNITION ENGINE WHICH COMPRISES THE OPERATION OF SAID ENGINE ON A FUEL CONSISTING ESSENTIALLY OF A RESIDUAL FUEL OIL AND SMALL AMOUNTS OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF LITHIUM NAPHTHENATE AND POTASSIUM NAPHTHENATE, SAID AMOUNT BEING SUFFICIENT TO REDUCE PISTON RING WEAR. 